Strapping Structure of Memory Circuit

ABSTRACT

A memory circuit includes a first memory cell and a second memory adjacent to the first memory cell. The first memory cell includes a first word line strapping line segment electrically coupled with a pass device of the first memory cell; and a second word line strapping line segment. The second memory cell includes a first word line strapping line segment; and a second word line strapping line segment electrically coupled with a pass device of the second memory cell. The first word line strapping line segment of the first memory cell and the first word line strapping line segment of the second memory cell are connected with each other at a first interconnection layer. The second word line strapping line segment of the first memory cell and the second word line strapping line segment of the second memory cell are connected with each other at the first interconnection layer.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.16,230,286, filed on Dec. 21, 2018, entitled “Strapping Structure ofMemory Circuit,” which is a continuation of U.S. patent application Ser.No. 15/887,210, filed on Feb. 2, 2018, and entitled “Strapping Structureof Memory Circuit”, now U.S. Pat. No. 10,163,886, issued on Dec. 25,2018 which is a divisional of U.S. patent application Ser. No.14/723,615, filed May 28, 2015, now U.S. Pat. No. 9,911,727 issued onMar. 6, 2018, and entitled “Strapping Structure of Memory Circuit” whichclaims priority to U.S. Provisional Patent Application No. 62/133,928,filed Mar. 16, 2015. The entire contents of the above-referencedapplications are incorporated by reference herein.

RELATED APPLICATIONS

The present application is related to U.S. patent application Ser. No.12/039,711, filed on Feb. 28, 2008, now U.S. Pat. No. 7,920,403 issuedon Apr. 5, 2011, and entitled “ROM CELL CONNECTION STRUCTURE,” and U.S.patent application Ser. No. 12/827,406, filed on Jun. 30, 2010, now U.S.Pat. No. 8,212,295 issued on Jul. 3, 2012, and entitled “ROM CELLCIRCUIT FOR FINFET DEVICES”. The entire contents of the above-referencedapplications are incorporated by reference herein.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs, where each generation has smaller and more complexcircuits than the previous generation. In the course of integratedcircuit evolution, functional density (i.e., the number ofinterconnected devices per chip area) has generally increased whilegeometry size (i.e., the smallest component or line that can be createdusing a fabrication process) has decreased. In some applications, amemory array includes rows of gate electrodes electrically connectingvarious rows of pass devices of memory cells of the memory array. Whenthe width of a conductive structure, such as the gate electrodestructures in the memory array, becomes smaller, the unit-lengthresistance of the conductive structure becomes greater. In someapplications, a digital signal transmitted on a conductive structure hasa longer rising or falling time when the unit-length resistance thereofbecomes greater. In some applications, the speed of turning on or offpass devices of different memory cells at different location of thememory array thus varies.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A is a schematic circuit diagram of two read-only memory (ROM)cells in a ROM circuit, in accordance with some embodiments.

FIG. 1B is a schematic circuit diagram of two read-only memory (ROM)cells in another ROM circuit, in accordance with some embodiments.

FIG. 2A is a top view of four ROM cells of a ROM circuit based on ROMcells of FIG. 1A, with all the depictions regarding components in andabove a second interconnection layer of the ROM circuit omitted, inaccordance with some embodiments.

FIG. 2B is a top view of the four ROM cells of FIG. 2A, with thedepictions regarding components from a first interconnection layer tothe second interconnection layer of the ROM circuit, in accordance withsome embodiments.

FIG. 3 is a cross-sectional view of the ROM circuit of FIGS. 2A and 2Btaken from reference line A-A′, in accordance with some embodiments.

FIG. 4 is a routing diagram of a portion of a memory circuit implementedbased on ROM cells of FIGS. 2A and 2B, in accordance with someembodiments.

FIG. 5 is a top view of a plurality of ROM cells and four strappingcells of a ROM circuit based on ROM cells of FIG. 1A or FIG. 1B, withthe depictions regarding some components of the ROM cells omitted, inaccordance with some embodiments.

FIG. 6 is a top view of a plurality of ROM cells and four strappingcells of another ROM circuit based on ROM cells of FIG. 1A or FIG. 1B,with the depictions regarding some components of the ROM cells omitted,in accordance with some embodiments.

FIG. 7 is a routing diagram of a memory device having strapping cells ofFIG. 5 and/or FIG. 6, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In accordance with some embodiments of the present disclosure, twoadjacent read-only memory (ROM) cells of the same row in a ROM circuitshare word line strapping structures implemented along the cellboundaries thereof at a first interconnection layer to reduce theequivalent unit-length resistance of the word line structure of the ROMcircuit. In accordance with some embodiments of the present disclosure,two adjacent strapping cells of the same column share at least onestrapping line at the first interconnection layer.

FIG. 1A is a schematic circuit diagram of two ROM cells 110[i] and110[i+1] in a ROM circuit 100A in accordance with some embodiments.Index “i” is a positive integer greater than zero.

ROM circuit 100A includes word lines WL[i] and WL[i+1] and a bit lineBL. Word line WL[i] is electrically coupled with ROM cell 110[i]; andword line WL[i+1] is electrically coupled with ROM cell 110[i+1]. Bitline BL is electrically coupled with ROM cells 110[i] and 110[i+1]. ROMcircuit 100A also includes an isolation device 122 that is shared by andconfigured to electrically isolate adjacent ROM cells. In someembodiments, ROM circuit 100A includes a plurality of ROM cell pairshaving a configuration similar to ROM cells 110[i] and 110[i+1].

ROM cell 110[i] includes a pass device 112[i] and a coding switch114[i]. Pass device 112[i] is an N-type transistor and also referred toas transistor 112[i]. A drain terminal of transistor 112[i] iselectrically coupled with bit line BL. A gate terminal of transistor112[i] is electrically coupled with word line WL[i]. A source terminalof transistor 112[i] is electrically coupled with coding switch 114[i].Coding switch 114[i] is disposed between transistor 112[i] and areference voltage node 116[i]. Coding switch 114[i] is set to be “open”or at a high resistance state to store a predetermined logic value, suchas a logic high value. Reference voltage node 116[i] is configured toreceive a reference voltage VSS. ROM cell 110[i+1] includes a passdevice 112[i+1] implemented by an N-type transistor and a coding switch114[i+1] coupled with bit line BL, word line WL[i+1], and referencevoltage node 116[i+1] in a manner similar to ROM cell 110[i], exceptcoding switch 114[i+1] is set to be “closed” or at a low resistancestate to store another predetermined logic value, such as a logic lowvalue.

In some embodiments, coding switches 114[i] and 114[i+1] are implementedby selectively forming or omitting one or more conductive via plugs orconductive lines between bit line BL and the corresponding pass device112[i] or 112[i+1]. In such a configuration, the logic values stored inROM cells 110[i] and 110[i+1] are hardwired after fabrication of the ROMcircuit 100A. In some embodiments, coding switches 114[i] and 114[i+1]are implemented by e-fuse devices. In such a configuration, the logicvalues stored in ROM cells 110[i] and 110[i+1] are programmable orone-time programmable after the ROM circuit 100A is fabricated.

Isolation device 122 is configured to electrically isolate codingswitches 114[i] and 114[i+1] of corresponding ROM cells 110[i] and110[i+1]. Isolation device 122 is implemented by an N-type transistorand also referred to as transistor 122. A gate terminal of transistor122 is electrically coupled with a reference voltage node 124. A firstdrain/source terminal of transistor 122 is electrically coupled withcoding switch 114[i] of ROM cell 110[i]. A second drain/source terminalof transistor 122 is electrically coupled with coding switch 114[i+1] ofROM cell 110[i+1]. Reference voltage node 124 is also configured toreceive reference voltage VSS. A voltage level of reference voltage VSSis set to be sufficient to turn off transistor 122.

FIG. 1B is a schematic circuit diagram of two read-only memory (ROM)cells 130[i] and 130[i+1] in another ROM circuit 100B in accordance withsome embodiments. Components of FIG. 1B that are the same or similar tothose of FIG. 1A are given the same reference labels, and detaileddescription thereof is thus omitted.

ROM circuit 100B includes word lines WL[i] and WL[i+1] and a bit lineBL. ROM circuit 100B also includes an isolation device 122 configured toelectrically isolate adjacent ROM cells. In some embodiments, ROMcircuit 100B includes a plurality of ROM cell pairs having aconfiguration similar to ROM cells 130[i] and 130[i+1].

ROM cell 130[i] includes a pass device 132[i] and a coding switch134[i]. Pass device 132[i] is an N-type transistor. A drain terminal oftransistor 132[i] is electrically coupled with coding switch 134[i]. Agate terminal of transistor 132[i] is electrically coupled with wordline WL[i]. A source terminal of transistor 112[i] is electricallycoupled with a reference voltage node 136[i]. Reference voltage node136[i] is configured to receive a reference voltage VSS. Coding switch134[i] is disposed between transistor 132[i] and bit line BL. Codingswitch 114[i] is set to be “open” or at a high resistance state to storea predetermined logic value, such as a logic high value. ROM cell130[i+1] includes a pass device 132[i+1] implemented by an N-typetransistor and a coding switch 134[i+1] coupled with bit line BL, wordline WL[i+1], and reference voltage node 136[i+1] in a manner similar toROM cell 130[i], except coding switch 134[i+1] is set to be “closed” orat a low resistance state to store another predetermined logic value,such as a logic low value.

In some embodiments, coding switches 134[i] and 134[i+1] are implementedby selectively forming or omitting one or more conductive via plugs orconductive lines. In such configuration, the logic values stored in ROMcells 130[i] and 130[i+1] are hardwired after fabrication of the ROMcircuit 100B. In some embodiments, coding switches 134[i] and 134[i+1]are implemented by e-fuse devices. In such a configuration, the logicvalues stored in ROM cells 130[i] and 130[i+1] are programmable orone-time programmable after the ROM circuit 100B is fabricated.

In some embodiments, the layout designs for implementing ROM circuit100A and ROM circuit 100B are the same at the transistor portion thereofand differ at the via and interconnection layers.

FIG. 2A is a top view of four ROM cells 210-11, 210-12, 210-21, and210-22 of a ROM circuit 200 based on ROM cells 110[i] and 110[i+1] ofFIG. 1A, with all the depictions regarding components in and above asecond interconnection layer of the ROM circuit 200 omitted, inaccordance with some embodiments. Details regarding the secondinterconnection layer of the ROM circuit 200 are illustrated inconjunction with FIG. 3.

ROM cells 210-11, 210-12, 210-21, and 210-22 are identified in FIG. 2Aby dotted lines representing reference cell boundaries thereof. FIG. 2Aalso depicts reference lines X₁, X₂, and X₃ extending along a Ydirection and reference lines Y₁, Y₂, and Y₃ extending along an Xdirection. Cell boundaries of ROM cell 210-11 extend along referenceline X₁, reference line X₂, reference line Y₁, and reference line Y₂.Cell boundaries of ROM cell 210-12 extend along reference line X₁,reference line X₂, reference line Y₂, and reference line Y₃. Cellboundaries of ROM cell 210-21 extend along reference line X₂, referenceline X₃, reference line Y₁, and reference line Y₂. Cell boundaries ofROM cell 210-22 extend along reference line X₂, reference line X₃,reference line Y₂, and reference line Y₃.

In some embodiments, a Y direction is also referred to as a columndirection of ROM circuit 200, and an X direction is also referred to asa row direction of ROM circuit 200.

ROM circuit 200 includes gate strips 222, 224, 226, and 228 extendingalong the X direction, fin structures 232 and 234 extending along the Ydirection, contact structures 242, 244, 252, 254, 256, and 258 extendingalong the X direction, and conductive lines 262, 264, 266, 268, 272,274, and 276 extending along the Y direction. In some embodiments,conductive lines 262, 264, 266, 268, 272, 274, and 276 are in a firstinterconnection layer of ROM circuit 200. The second interconnectionlayer is disposed above the first interconnection layer. Detailsregarding the first interconnection layer of the ROM circuit 200 areillustrated in conjunction with FIG. 3.

ROM circuit 200 also includes various via plugs at a first via pluglayer (labeled as V1 or V1_Coding) and gate contact structures GCdisposed to electrically connecting various gate strips, contactstructures, or conductive lines.

Fin structures 232 and 234 and conductive lines 262, 264, 266, and 268extend beyond ROM cells 210-11, 210-12, 210-21, and 210-22 and areusable as parts of the ROM cells of ROM circuit 200 that are notdepicted in FIG. 2A.

ROM cell 210-11 includes a first gate structure 222 a, a second gatestructure 226 a, a first word line strapping line segment 274 a, asecond word line strapping line segment 272 a, a bit line segment 262 a,and a reference voltage line segment 264 a. First gate structure 222 ais a portion of gate strip 222 that is within an area from referenceline X₁ to reference line X₂. Second gate structure 226 a is a portionof gate strip 226 that is within an area from reference line X₁ toreference line X₂. First word line strapping line segment 274 a is aportion of conductive line 274 that is within an area from referenceline Y₁ to reference line Y₂. Second word line strapping line segment272 a is a portion of conductive line 272 that is within an area fromreference line Y₁ to reference line Y₂. Bit line segment 262 a is aportion of conductive line 262 that is within an area from referenceline Y₁ to reference line Y₂. Reference voltage line segment 264 a is aportion of conductive line 264 that is within an area from referenceline Y₁ to reference line Y₂. ROM cell 210-11 also includes a portion offin structure 232 within an area from reference line Y₁ to referenceline Y₂.

In some embodiments, ROM cell 210-11 corresponds to ROM cell 110[i] inFIG. 1A, and Bit line segment 262 a corresponds to bit line BL in FIG.1A. In some embodiments, reference voltage line segment 264 acorresponds to reference voltage nodes 116[i] and 124 and is configuredto receive reference voltage VSS. Fin structures 232, first gatestructure 222 a, and contact structures 242 and 254 together correspondto pass device 112[i] (FIG. 1A). Fin structures 232, second gatestructure 226 a, and contact structure 254, and a counterpart contactstructure (not shown) on an opposite side of second gate structure 226 atogether correspond to isolation device 122 (FIG. 1A).

First gate structure 222 a corresponds to the gate terminal oftransistor 112[i]. Contact structure 242 corresponds to drain terminalof transistor 112[i] and is electrically connected with bit line segment262 a through a corresponding via plug V1. Contact structure 254corresponds to source terminal of transistor 112[i] and is electricallyconnected with reference voltage line segment 264 a through acorresponding via plug V1_Coding to store a logic low value.

Second gate structure 226 a corresponds to the gate terminal oftransistor 122 and is electrically connected with reference voltage linesegment 264 a through a corresponding via plug V1 and a correspondinggate contact structure GC to turn off transistor 122. Contact structure254 corresponds to the first drain/source terminal of transistor 122.The counterpart contact structure (not shown) on the opposite side ofsecond gate structure 226 a corresponds to the second drain/sourceterminal of transistor 122.

First word line strapping line segment 274 a extends along referenceline X₂ and is electrically connected with first gate structure 222 athrough a via plug V1-1 and a gate contact structure GC-1. Second wordline strapping line segment 272 a extends along reference line X₁ and isfree from being electrically connected with first gate structure 222 awithin the cell boundaries of ROM cell 210-11.

ROM cell 210-12 includes a first gate structure 224 a, a second gatestructure 228 a, a first word line strapping line segment 274 b, asecond word line strapping line segment 272 b, a bit line segment 262 b,and a reference voltage line segment 264 b. First gate structure 224 ais a portion of gate strip 224 that is within an area from referenceline X₁ to reference line X₂. Second gate structure 228 a is a portionof gate strip 228 that is within an area from reference line X₁ toreference line X₂. First word line strapping line segment 274 b is aportion of conductive line 274 that is within an area from referenceline Y₂ to reference line Y₃. Second word line strapping line segment272 b is a portion of conductive line 272 that is within an area fromreference line Y₂ to reference line Y₃. Bit line segment 262 b is aportion of conductive line 262 that is within an area from referenceline Y₂ to reference line Y₃. Reference voltage line segment 264 b is aportion of conductive line 264 that is within an area from referenceline Y₂ to reference line Y₃. ROM cell 210-12 also includes a portion offin structure 232 within an area from reference line Y₂ to referenceline Y₃.

First gate structure 224 a, second gate structure 228 a, first word linestrapping line segment 274 b, second word line strapping line segment272 b, bit line segment 262 b, and reference voltage line segment 264 bof ROM cell 210-12 correspond to first gate structure 222 a, second gatestructure 224 a, first word line strapping line segment 274 a, secondword line strapping line segment 272 a, bit line segment 262 a, andreference voltage line segment 264 a of ROM cell 210-11, and detaileddescription thereof is thus omitted. Contact structure 242 correspondsto a drain terminal of the pass device of ROM cell 210-12. Contactstructure 252 corresponds to a source terminal of the pass device of ROMcell 210-12 and a drain/source terminal of isolation device of ROM cell210-12.

Word line strapping line segment 274 a and word line strapping linesegment 274 b are connected with each other at the first interconnectionlayer of the ROM circuit 200. Word line strapping line segment 272 a andword line strapping line segment 272 b are connected with each other atthe first interconnection layer of the ROM circuit 200.

Bit line segment 262 a and the bit line segment 262 b are connected witheach other at the first interconnection layer of the ROM circuit 200.Reference voltage line segment 264 a and the reference voltage linesegment 264 b are connected with each other at the first interconnectionlayer of the ROM circuit 200.

Compared with ROM cell 210-11, first word line strapping line segment274-b is free from being electrically connected with first gatestructure 224 a within the cell boundaries of ROM cell 210-12. Also,second word line strapping line segment 272 b is electrically connectedwith first gate structure 224 a through a via plug V1-2 and a gatecontact structure GC-2.

ROM cell 210-21 includes a first gate structure 222 b, a second gatestructure 226 b, a first word line strapping line segment 276 a, asecond word line strapping line segment 274 a, a bit line segment 266 a,and a reference voltage line segment 268 a. First gate structure 222 bis a portion of gate strip 222 that is within an area from referenceline X₂ to reference line X₃. Second gate structure 226 b is a portionof gate strip 226 that is within an area from reference line X₂ toreference line X₃. Gate structures 222 a and 222 b are connected witheach other. Gate structures 224 a and 224 b are connected with eachother.

First word line strapping line segment 276 a is a portion of conductiveline 276 that is within an area from reference line Y₁ to reference lineY₂. Second word line strapping line segment 274 a is the same contactstructure used as first word line strapping line segment 274 a of ROMcell 210-11. Bit line segment 266 a is a portion of conductive line 266that is within an area from reference line Y₁ to reference line Y₂.Reference voltage line segment 268 a is a portion of conductive line 268that is within an area from reference line Y₁ to reference line Y₂. ROMcell 210-21 also includes a portion of fin structure 234 within an areafrom reference line Y₁ to reference line Y₂.

First gate structure 222 b, second gate structure 226 b, first word linestrapping line segment 276 a, second word line strapping line segment274 a, bit line segment 266 a, and reference voltage line segment 268 aof ROM cell 210-21 correspond to first gate structure 222 a, second gatestructure 224 a, first word line strapping line segment 274 a, secondword line strapping line segment 272 a, bit line segment 262 a, andreference voltage line segment 264 a of ROM cell 210-11, and detaileddescription thereof is thus omitted. Contact structure 244 correspondsto a drain terminal of the pass device of ROM cell 210-21. Contactstructure 258 corresponds to a source terminal of the pass device of ROMcell 210-21 and a drain/source terminal of isolation device of ROM cell210-21.

Compared with ROM cell 210-11, first word line strapping line segment276 a is free from being electrically connected with first gatestructure 222 b within the cell boundaries of ROM cell 210-21. Also,second word line strapping line segment 274 a is electrically connectedwith first gate structure 222 b through via plug V1-1 and gate contactstructure GC-1. Contact structure 258 is not electrically connected withreference voltage line segment 268 a to store a logic high value.

ROM cell 210-22 includes a first gate structure 224 b, a second gatestructure 228 b, a first word line strapping line segment 276 b, asecond word line strapping line segment 274 b, a bit line segment 266 b,and a reference voltage line segment 268 b. First gate structure 224 bis a portion of gate strip 226 that is within an area from referenceline X₂ to reference line X₃. Second gate structure 228 b is a portionof gate strip 228 that is within an area from reference line X₂ toreference line X₃. Gate structures 226 a and 226 b are connected witheach other. Gate structures 228 a and 228 b are connected with eachother.

First word line strapping line segment 276 b is a portion of conductiveline 276 that is within an area from reference line Y₂ to reference lineY₃. Second word line strapping line segment 274 b is a portion ofconductive line 274 that is within an area from reference line Y₂ toreference line Y₃. Second word line strapping line segment 274 b is thesame contact structure used as first word line strapping line segment274 b of ROM cell 210-12. Bit line segment 266 b is a portion ofconductive line 266 that is within an area from reference line Y₂ toreference line Y₃. Reference voltage line segment 268 b is a portion ofconductive line 268 that is within an area from reference line Y₂ toreference line Y₃. ROM cell 210-22 also includes a portion of finstructure 234 within reference line Y₂ to reference line Y₃.

First gate structure 224 b, second gate structure 228 b, first word linestrapping line segment 276 b, second word line strapping line segment274 b, bit line segment 266 b, and reference voltage line segment 268 bof ROM cell 210-22 correspond to first gate structure 222 a, second gatestructure 224 a, first word line strapping line segment 274 a, secondword line strapping line segment 272 a, bit line segment 262 a, andreference voltage line segment 264 a of ROM cell 210-11, and detaileddescription thereof is thus omitted. Contact structure 244 correspondsto a drain terminal of the pass device of ROM cell 210-22. Contactstructure 256 corresponds to a source terminal of the pass device of ROMcell 210-22 and a drain/source terminal of isolation device of ROM cell210-22.

Word line strapping line segment 276 a and word line strapping linesegment 276 b are connected with each other at the first interconnectionlayer of the ROM circuit 200. Bit line segment 266 a and the bit linesegment 266 b are connected with each other at the first interconnectionlayer of the ROM circuit 200. Reference voltage line segment 268 a andthe reference voltage line segment 268 b are connected with each otherat the first interconnection layer of the ROM circuit 200.

Compared with ROM cell 210-11, first word line strapping line segment276 b is also electrically connected with first gate structure 224 bthrough a via plug V1-3 and a gate contact structure GC-3. Second wordline strapping line segment 274 b is free from being electricallyconnected with first gate structure 224 b within the cell boundaries ofROM cell 210-22.

Furthermore, fin structures 232 includes three fin structures extendingalong Y direction, and fin structures 234 includes three fin structuresextending along Y direction. In some embodiments, fin structures 232 andfin structures 234 each have more or less than three fin structures. Insome embodiments, fin structures 232 and fin structures 234 aremanufactured by forming a plurality of parallel find structures thanremoving one or more fin structures that are within the gap region 236.In some embodiments, a width of gap region 236 is sufficient toaccommodate word line strapping line segments and corresponding viaplugs for forming a word line strapping structure. In suchcircumstances, inclusion of word line strapping structures asillustrated in FIG. 2A does not demand for additional area penalty forROM circuit 200.

FIG. 2B is a top view of the four ROM cells 210-11, 210-12, 210-21, and210-22 of FIG. 2A, with the depictions regarding components from thefirst interconnection layer to the second interconnection layer of theROM circuit 200, in accordance with some embodiments. Components thatare the same or similar to those in FIG. 2A are given the same referencenumbers, and detailed description thereof is thus omitted.

ROM circuit 200 further includes conductive lines 282, 284, 286, and 288extending along X direction. In some embodiments, conductive lines 282,284, 286, and 288 are in the second interconnection layer of ROM circuit200. ROM circuit 200 also includes various via plugs at a second viaplug layer (labeled as V2) disposed to electrically connecting variousconductive lines between the first interconnection layer and the secondinterconnection layer of ROM circuit 200.

ROM cell 210-11 includes a word line segment 282 a and a referencevoltage line segment 286 a. Word line segment 282 a is a portion ofconductive line 282 that is within an area from reference line X₁ toreference line X₂. Reference voltage line segment 286 a is a portion ofconductive line 286 that is within an area from reference line X₁ toreference line X₂. Word line segment 282 a corresponds to word lineWL[i] in FIG. 1A. Reference voltage line segment 286 a corresponds toreference voltage nodes 116[i] and 124 and is configured to receivereference voltage VSS.

Word line segment 282 a is electrically connected with first word linestrapping line segment 274 a through a via plug V2-1 and is free frombeing electrically connected with second word line strapping linesegment 272 a within the cell boundaries of ROM cell 210-11. Referencevoltage line segment 286 a is electrically connected with conductiveline 264 through a corresponding via plug V2.

ROM cell 210-12 includes a word line segment 284 a and a referencevoltage line segment 288 a. Word line segment 284 a is a portion ofconductive line 284 that is within an area from reference line X₁ toreference line X₂. Reference voltage line segment 288 a is a portion ofconductive line 288 that is within an area from reference line X₁ toreference line X₂. Word line segment 284 a and reference voltage linesegment 288 a correspond to word line segment 282 a and referencevoltage line segment 286 a of ROM cell 210-11, and detailed descriptionthereof is thus omitted.

Compared with ROM cell 210-11, word line segment 284 a is electricallyconnected with second word line strapping line segment 272 b through avia plug V2-2 and is not electrically connected with first word linestrapping line segment 274 b within the cell boundaries of ROM cell210-12. Reference voltage line segment 288 a is electrically connectedwith conductive line 264 through a corresponding via plug V2.

ROM cell 210-21 includes a word line segment 282 b and a referencevoltage line segment 286 b. Word line segment 282 b is a portion ofconductive line 282 that is within an area from reference line X₂ toreference line X₃. Reference voltage line segment 286 b is a portion ofconductive line 286 that is within an area from reference line X₂ toreference line X₃. Word line segments 282 a and 282 b are connected witheach other at the second interconnection layer of ROM circuit 200.Reference voltage line segments 286 a and 286 b are connected with eachother at the second interconnection layer of ROM circuit 200. Word linesegment 282 b and reference voltage line segment 284 b correspond toword line segment 282 a and reference voltage line segment 286 a of ROMcell 210-11, and detailed description thereof is thus omitted.

Compared with ROM cell 210-11, word line segment 282 b is electricallyconnected with second word line strapping line segment 274 a through viaplug V2-1, which is the same word line strapping line segment configuredas first word line strapping line segment 274 a of ROM cell 210-11.Also, word line segment 282 b is free from being electrically connectedwith first word line strapping line segment 276 a within the cellboundaries of ROM cell 210-21. Reference voltage line segment 286 b iselectrically connected with conductive line 268 through a correspondingvia plug V2.

ROM cell 210-22 includes a word line segment 284 b and a referencevoltage line segment 288 b. Word line segment 284 b is a portion ofconductive line 284 that is within an area from reference line X₂ toreference line X₃. Reference voltage line segment 288 b is a portion ofconductive line 288 that is within an area from reference line X₂ toreference line X₃. Word line segments 284 a and 284 b are connected witheach other at the second interconnection layer of ROM circuit 200.Reference voltage line segments 288 a and 288 b are connected with eachother at the second interconnection layer of ROM circuit 200. Word linesegment 284 b and reference voltage line segment 288 b correspond toword line segment 282 a and reference voltage line segment 286 a of ROMcell 210-11, and detailed description thereof is thus omitted.

Compared with ROM cell 210-11, word line segment 284 b is electricallyconnected with first word line strapping line segment 276 b through avia plug V2-3 and is free from being electrically connected with secondword line strapping line segment 274 b within the cell boundaries of ROMcell 210-22. Second word line strapping line segment 274 b is configuredas first word line strapping line segment 274 b of ROM cell 210-12.Reference voltage line segment 288 b is electrically connected withconductive line 268 through a corresponding via plug V2.

FIG. 3 is a cross-sectional view of ROM circuit 200 of FIGS. 2A and 2Btaken from reference line A-A′ in accordance with some embodiments.Components in FIG. 3 that are the same or similar to those in FIGS. 2Aand 2B are given the same reference numbers, and detailed descriptionthereof is thus omitted. Reference line L₁ corresponds to the positionwhere reference line X₁ intersects reference line A-A′. Reference lineL₂ corresponds to the position where reference line X₂ intersectsreference line A-A′. Reference line L₃ corresponds to the position wherereference line X₃ intersects reference line A-A′.

ROM circuit 200 includes a substrate 310, a plurality of fin structures232 and 234 over substrate 310, an isolation layer 320 over substrate310 and surrounding fin structures 232 and 234, and a gate strip 224over isolation layer 320 and fin structures 232 and 234. ROM circuit 200also includes gate contact structures GC-2 and GC-3 over gate strip 224,via plugs V1-2 and V1-3 at a first via layer of ROM circuit 200 and overgate contact structures GC-2 and GC-3, conductive lines 262, 264, 266,268, 272, 274, and 276 at a first interconnection layer of ROM circuit200 and over the first via layer, via plugs V2-2 and V2-3 at a secondvia layer of ROM circuit 200 and over the first interconnection layer,and conductive line 284 at a second interconnection layer of ROM circuit200 and over the second via layer.

Conductive line 284 is electrically coupled with gate strip 224 throughvia plug V2-2, conductive line 272, via plug V1-2, and gate contactstructure GC-2 stacked along reference line L₁. Conductive line 284 isalso electrically coupled with gate strip 224 through via plug V2-3,conductive line 276, via plug V1-3, and gate contact structure GC-3stacked along reference line L3.

In some embodiments, substrate 310 includes: an elementary semiconductorsuch as silicon or germanium in crystal, polycrystalline, or anamorphous structure; a compound semiconductor including silicon carbide,gallium arsenide, gallium phosphide, gallium nitride, indium phosphide,indium arsenide, and/or indium antimonide; an alloy semiconductorincluding SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; orcombinations thereof. In at least one embodiment, substrate 310 is analloy semiconductor substrate having a gradient SiGe feature in whichthe Si and Ge composition change from one ratio at one location toanother ratio at another location of the gradient SiGe feature. Inanother embodiment, the alloy SiGe is formed over a silicon substrate.In yet another embodiment, a SiGe substrate is strained. In someembodiments, substrate 310 is a semiconductor on insulator. In someexamples, substrate 310 includes an epitaxial layer or a buried layer.In other examples, substrate 310 has a multilayer structure, orsubstrate 310 includes a multilayer compound semiconductor structure.

In some embodiments, gate strips 222, 224, 226, and 228 are polysilicongate structures or metal gate structures. In some embodiments, finstructures 232 and 234 are doped semiconductor materials usable asactive regions or various transistors of ROM circuit 200. In someembodiments, contact structures 242, 244, 252, 254, 256, and 258 includea material such as polysilicon, silicide, or metal.

In some embodiments, via plugs V1, V1_Coding, or V2 has a materialincludes aluminum, copper, tungsten, a combination thereof, or othersuitable materials. In some embodiments, gate contact structures GC hasa material includes polysilicon, silicide, aluminum, copper, tungsten, acombination thereof, or other suitable materials. In some embodiments,conductive lines 262, 264, 266, 268, 272, 274, 276, and/or 284 has amaterial includes aluminum, copper, a combination thereof, or othersuitable materials.

FIG. 4 is a routing diagram of a portion of a memory circuit 400implemented based on ROM cells 210-11, 210-12, 210-21- and 210-22 ofFIGS. 2A and 2B in accordance with some embodiments.

Memory circuit 400 includes a plurality of ROM cells arranged intocolumns COL[n−1], COL[n], COL[n+1], COL[n+2], and COL[n+3] and rowsROW[m−3], ROW[m−2], ROW[m−1], ROW[m], ROW[m+1], and ROW[m+2]. Each ROMcell of memory circuit 400 has a configuration similar to one of ROMcells 210-11, 210-12, 210-21, and 210-22 depicted in FIGS. 2A and 2B.Memory circuit 400 further includes a plurality of bit lines BL[n−1],BL[n], BL[n+1], BL[n+2], and BL[n+2] extending along direction Y at afirst interconnection layer of memory circuit 400, a plurality of wordlines WL[m−3], WL[m−2], WL[m−1], WL[m], WL[m+1], and WL[m+2] extendingalong the X direction at a second interconnection layer of memorycircuit 400, a first set of reference voltage lines 410[n−1], 410[n],410[n+1], 410[n+2], and 410[n+2] extending along the Y direction at thefirst interconnection layer, and a second set of reference voltage lines420[k] and 420[k−1] extending along the X direction at the secondinterconnection layer. Indices “m,” “n,” “k” are integers usable toidentify individual components in FIG. 4.

Memory circuit 400 includes a plurality of word line strappingstructures (depicted as rectangles in FIG. 4) corresponding to word linestrapping segments of FIG. 2A and a plurality of via plugs V1 andV1_Coding corresponding to via plugs V1 and V1_Coding of FIG. 2A. Area430 corresponds to ROM cells 210-11, 210-12, 210-21, and 210-22 of FIGS.2A and 2B. Memory circuit 400 is implemented by an array of duplicatesof area 430 with via plugs V1_Coding selectively placed to record data.

Compared with FIG. 2, word lines WL[m−3]˜WL[m+2] also correspond to theposition of the gate structures of pass devices of memory circuit 400,and reference voltage lines 420[k] and 420[k−1] also correspond to theposition of the gate structures of isolation devices of memory circuit400.

As depicted in FIG. 4, in each row ROW[m−3]˜ROW[m+2], every two adjacentROM cells shared one word line stripping structure that is electricallyconnected to the corresponding word line WL[m−3]˜WL[m+2]. Also, eachword line strapping structure does not extend beyond two corresponding,adjacent reference voltage lines 420[k] and 420[K−1]. In each columnCOL[n−1]˜COL[n+3], every two adjacent ROM cells between twocorresponding, adjacent reference voltage lines 420[k] and 420[K−1] hastwo word line strapping structures: one word line strapping structurefor a corresponding one word line of the two adjacent ROM cells.

Memory circuit 200 and 400 illustrated in conjunction with FIGS. 2A˜4are based on memory circuit 100A of FIG. 1A. In some embodiments, memorycircuit 200 and 400 are modified to implement memory circuit 100B ofFIG. 1A. For example, for memory cell 210-11, contact structure 242corresponds to the source terminal of transistor 132[i] and iselectrically connected with conductive line 264 through a correspondingvia plug V1 instead of conductive line 262; and contact structure 254corresponds to the drain terminal of transistor 132[i] and iselectrically connected with conductive line 262 through a correspondingvia plug V1_Coding instead of conductive line 264. For implementing amemory circuit based on memory circuit 100B, ROM cells 210-12, 210-21,and 210-22 are modified in a manner similar to the modification for ROMcell 210-11 illustrated above.

FIG. 5 is a top view of a plurality of ROM cells and four strappingcells of a ROM circuit 500 based on ROM cells of FIG. 1A or FIG. 1B,with the depictions regarding some components of the ROM cells omitted,in accordance with some embodiments. In some embodiments, ROM cells ofFIG. 5 are different from ROM cells of FIG. 1A or FIG. 1B.

Memory circuit 500 includes a plurality of ROM cells arranged intocolumns COL[1], COL[2], COL[3], and COL[4] and rows ROW[1], ROW[2],ROW[3], and ROW[4]. Memory circuit 500 also includes a column ofstrapping cells COL[S]. In some embodiments, ROM cells memory circuit500 are grouped into several memory arrays, where columns COL[1] andCOL[2] belong to one of the memory arrays, and columns COL[3] and COL[4]belong to another one of the memory arrays. FIG. 5 depicts cellboundaries of various cells with fine, dotted lines.

Memory circuit 500 includes further includes bit lines BL[1], BL[2],BL[3], and BL[4] extending along direction Y at a first interconnectionlayer of memory circuit 500, a plurality of word lines WL[1], WL[1],WL[3], and WL[4] extending along the X direction at a secondinterconnection layer of memory circuit 500, a first set of referencevoltage lines 510[1], 510[2], 510[3], and 510[4] extending along the Ydirection at the first interconnection layer, and a second set ofreference voltage lines 520[1], 520[2], and 520[3] extending along the Xdirection at the second interconnection layer. Memory circuit 500 alsoincludes gate strips 530[1], 530[2], 530[3], and 530[4] corresponding togate electrodes of pass devices of memory circuit 500 and gate strips532[1], 532[2], and 532[3] corresponding to gate electrodes of isolationdevices of memory circuit 500.

In some embodiments, each ROM cell has a configuration similar to one ofROM cells 210-11, 210-12, 210-21- and 210-22 illustrated in FIGS. 2A and2B, and detailed description thereof is thus omitted. In someembodiments, each ROM cell has a configuration similar to one of ROMcells 210-11, 210-12, 210-21, and 210-22 illustrated in FIGS. 2A and 2Bbut free from having conductive lines 272, 274, and 276 andcorresponding via plugs for forming word line strapping structures.

A strapping cell 542S (not labeled, positioned at row ROW[1] and columnCOL[S]) is between ROM cell 542L (not labeled, positioned at row ROW[1]and column COL[2]) and ROM cell 542R (not labeled, positioned at rowROW[1] and column COL[3]). Strapping cell 542S has a first gatestructure that is a portion of gate strip 530[1] within the cellboundaries of strapping cell 542S. The first gate structure of strappingcell 542S is connected with a gate structure of a pass device of ROMcell 542L and a gate structure of a pass device of ROM cell 542R.Strapping cell 542S has a word line segment that is a portion of wordline WL[1] within the cell boundaries of strapping cell 542S. The wordline segment of strapping cell 542S is connected with a word linesegment of ROM cell 542L and a word line segment of ROM cell 542R.

Strapping cell 542S has a first word line strapping line segment 552 aat the first interconnection layer of ROM circuit 500 and a second wordline strapping line segment 554 a at the first interconnection layer ofROM circuit 500. First word line strapping line segment 552 a isconnected with the first gate structure of strapping cell 542S through acorresponding gate contact structures GC and a corresponding via plug V1at a first via layer. First word line strapping line segment 552 a isconnected with the word line segment of strapping cell 542S through acorresponding via plug V2 at a second via layer. Therefore, a portion ofword line WL[1], i.e., the word line segment of strapping cell 542S, iselectrically coupled with gate strip 530[1] within the cell boundariesof strapping cell 542S.

Another strapping cell 544S (not labeled, positioned at row ROW[2] andcolumn COL[S]) is between ROM cell 544L (not labeled, positioned at rowROW[2] and column COL[2]) and ROM cell 544R (not labeled, positioned atrow ROW[2] and column COL[3]). Strapping cell 544S has a first gatestructure that is a portion of gate strip 530[2] within the cellboundaries of strapping cell 544S. The first gate structure of strappingcell 544S is connected with a gate structure of a pass device of ROMcell 544L and a gate structure of a pass device of ROM cell 544R.Strapping cell 544S has a word line segment that is a portion of wordline WL[2] within the cell boundaries of strapping cell 544S. The wordline segment of strapping cell 544S is connected with a word linesegment of ROM cell 544L and a word line segment of ROM cell 544R.

Strapping cell 544S has a first word line strapping line segment 552 bat the first interconnection layer of ROM circuit 500 and a second wordline strapping line segment 554 b at the first interconnection layer ofROM circuit 500. Word line strapping line segments 552 a and 552 b areconnected with each other, and word line strapping line segments 554 aand 554 b are connected with each other. Second word line strapping linesegment 554 b is connected with the first gate structure of strappingcell 544S through a corresponding gate contact structures GC and acorresponding via plug V1 at the first via layer. First word linestrapping line segment 554 b is connected with the word line segment ofstrapping cell 544S through a corresponding via plug V2 at the secondvia layer. Therefore, a portion of word line WL[2], i.e., the word linesegment of strapping cell 544S, is electrically coupled with gate strip530[2] within the cell boundaries of strapping cell 544S.

Strapping cell 546S (not labeled, positioned at row ROW[3] and columnCOL[S]) has word line strapping line segments 556 a and 558 acorresponding to word line strapping line segments 552 a and 554 a ofstrapping cell 542S. Strapping cell 548S (not labeled, positioned at rowROW[4] and column COL[S]) has word line strapping line segments 556 band 558 b corresponding to word line strapping line segments 552 b and554 b of strapping cell 544S. Strapping cell 546S and strapping cell548S has a configuration as a duplicate of strapping cell 542S andstrapping cell 544S, and detailed description thereof is thus omitted.In some embodiments, strapping cell 546S and strapping cell 548S has aconfiguration as a mirrored configuration of strapping cell 542S andstrapping cell 544S, where word line WL[3] is electrically coupled withgate strip 530[3] through word line strapping line segment 558 a, andword line WL[4] is electrically coupled with gate strip 530[4] throughword line strapping line segment 556 b.

FIG. 6 is a top view of a plurality of ROM cells and four strappingcells of another ROM circuit 600 based on ROM cells of FIG. 1A or FIG.1B, with the depictions regarding some components of the ROM cellsomitted, in accordance with some embodiments. In some embodiments, ROMcells of FIG. 5 are different from ROM cells of FIG. 1A or FIG. 1B.

Components in FIG. 6 that are the same or similar to those in FIG. 5 aregiven the same reference numbers, and detailed description thereof isthus omitted. FIG. 6 also depicts cell boundaries of various cells withfine, dotted lines.

A strapping cell 612S (not labeled, positioned at row ROW[1] and columnCOL[S]) is between ROM cell 612L (not labeled, positioned at row ROW[1]and column COL[2]) and ROM cell 612R (not labeled, positioned at rowROW[1] and column COL[3]). The cell boundaries of strapping cell 612Sincludes a left boundary along a reference line X₄ and a right boundaryalong a reference line X₅. Strapping cell 612S has a first gatestructure that is a portion of gate strip 530[1] within the cellboundaries of strapping cell 612S. The first gate structure of strappingcell 612S is connected with a gate structure of a pass device of ROMcell 612L and a gate structure of a pass device of ROM cell 612R.Strapping cell 612S has a second gate structure that is a portion ofgate strip 532[1] within the reference line X₄ and the reference lineX₅. The second gate structure of strapping cell 612S is connected with agate structure of an isolation device of ROM cell 612L and a gatestructure of an isolation device of ROM cell 612R. Strapping cell 612Shas a word line segment that is a portion of word line WL[1] within thecell boundaries of strapping cell 612S. The word line segment ofstrapping cell 612S is connected with a word line segment of ROM cell612L and a word line segment of ROM cell 612R.

Strapping cell 612S has an isolation gate strapping line segment 622 aat the first interconnection layer of ROM circuit 600 and a word linestrapping line segment 632 at the first interconnection layer of ROMcircuit 600.

Word line strapping line segment 632 is connected with the first gatestructure of strapping cell 612S through a corresponding gate contactstructures GC and a corresponding via plug V1 at a first via layer. Wordline strapping line segment 632 is also connected with the word linesegment of strapping cell 612S through a corresponding via plug V2 at asecond via layer. Therefore, a portion of word line WL[1], i.e., theword line segment of strapping cell 612S, is electrically coupled withgate strip 530[1] within the cell boundaries of strapping cell 612S.

Isolation gate strapping line segment 622 a is connected with the secondgate structure of strapping cell 6125 through a corresponding gatecontact structures GC and a corresponding via plug V1 at the first vialayer. Isolation gate strapping line segment 622 a is also connectedwith the reference line 520[1] through a corresponding via plug V2 atthe second via layer.

Another strapping cell 6145 (not labeled, positioned at row ROW[2] andcolumn COL[S]) is between ROM cell 614L (not labeled, positioned at rowROW[2] and column COL[2]) and ROM cell 614R (not labeled, positioned atrow ROW[2] and column COL[3]). Strapping cell 6145 has a first gatestructure that is a portion of gate strip 530[2] within the cellboundaries of strapping cell 544S. The first gate structure of strappingcell 544S is connected with a gate structure of a pass device of ROMcell 614L and a gate structure of a pass device of ROM cell 614R.Strapping cell 6145 has a second gate structure that is a portion ofgate strip 532[2] within the reference line X₄ and the reference lineX₅. The second gate structure of strapping cell 6145 is connected with agate structure of an isolation device of ROM cell 614L and a gatestructure of an isolation device of ROM cell 614R. Strapping cell 6145has an isolation gate strapping line segment 622 b at the firstinterconnection layer of ROM circuit 600 and a word line strapping linesegment 634 at the first interconnection layer of ROM circuit 600.

Word line strapping line segment 634 is connected with the first gatestructure of strapping cell 614S through a corresponding gate contactstructures GC and a corresponding via plug V1 at the first via layer.Word line strapping line segment 634 is also connected with the wordline segment of strapping cell 614S through a corresponding via plug V2at the second via layer. Therefore, a portion of word line WL[2], i.e.,the word line segment of strapping cell 614S, is electrically coupledwith gate strip 530[2] within the cell boundaries of strapping cell614S.

Isolation gate strapping line segment 622 b is connected with the secondgate structure of strapping cell 614S through a corresponding gatecontact structures GC and a corresponding via plug V1 at the first vialayer. Isolation gate strapping line segment 622 b is also connectedwith the reference line 520[2] through a corresponding via plug V2 atthe second via layer. Isolation gate strapping line segment 622 a andIsolation gate strapping line segment 622 b are connected with eachother.

Strapping cell 616S (not labeled, positioned at row ROW[3] and columnCOL[S]) has isolation gate strapping line segment 622 c and word linestrapping line segment 636 corresponding to isolation gate strappingline segment 622 a and word line strapping line segment 632 of strappingcell 612S. Strapping cell 616S and strapping cell 614S shares the sameisolation device. Isolation gate strapping line segment 622 b andIsolation gate strapping line segment 622 c are connected with eachother. Strapping cell 618S (not labeled, positioned at row ROW[4] andcolumn COL[S]) has isolation gate strapping line segment 622 d and wordline strapping line segment 638 corresponding to isolation gatestrapping line segment 622 b and word line strapping line segment 634 ofstrapping cell 614S. Isolation gate strapping line segment 622 c andIsolation gate strapping line segment 622 d are connected with eachother. Strapping cell 616S and strapping cell 618S have a configurationas a duplicate of strapping cell 612S and strapping cell 614S, anddetailed description thereof is thus omitted.

FIG. 7 is a routing diagram of a memory device 700 having strappingcells of FIG. 5 and/or FIG. 6, in accordance with some embodiments.

Memory device 700 includes memory cell arrays 712, 714, 716, and 718 andcolumn edge cells 722 a, 722 b, 724 a, 724 b, 726 a, 726 b, 728 a, and728 b. Each memory cell array of memory cell arrays 712, 714, 716, and718 has M columns and N rows of ROM cells. M and N are positiveintegers. In some embodiments, each ROM cell of memory cell arrays 712,714, 716, and 718 has a configuration similar to one of ROM cells210-11, 210-12, 210-21, and 210-22 illustrated in FIGS. 2A and 2B. Insome embodiments, each memory cell of memory cell array 712, 714, 716,or 718 has a configuration similar to one of ROM cells 210-11, 210-12,210-21, and 210-22 illustrated in FIGS. 2A and 2B with the omission ofconductive lines 272, 274, and 276 and corresponding via plugs forforming word line strapping structures.

Memory cell array 712 is placed between column edge cells 722 a and 722b along a column direction (e.g., the Y direction); memory cell array714 is placed between column edge cells 724 a and 724 b along the Ydirection; memory cell array 716 is placed between column edge cells 726a and 726 b along the Y direction; and memory cell array 718 is placedbetween column edge cells 728 a and 728 b along the Y direction. Fourmemory cell arrays 712, 714, 716, and 718 are depicted as a non-limitingexample. In some embodiments, memory device 700 includes more or lessthan four memory cell arrays.

Memory device 700 further includes dummy cell regions (identified as“DUMMY” in FIG. 7) and columns of strapping cells 732, 734, and 736 andtwo columns of edge strapping cells 742 and 744 between various dummycell regions. Memory cell array 712 is placed between edge strappingcells 742 and strapping cells 732 along a row direction (e.g., the Xdirection); memory cell arrays 714 is placed between a column ofstrapping cells 732 and a column of strapping cells 734 along the Ydirection; memory cell arrays 716 is placed between a column ofstrapping cells 734 and a column of strapping cells 736 along the Ydirection; and memory cell arrays 718 is placed between a column ofstrapping cells 736 and a column of edge strapping cells 744 along the Ydirection.

In some embodiments, memory device 700 includes a plurality of gatestrip and word lines extending along the X direction throughout at leastmemory cell arrays 712, 714, 716, and 718 and the columns of strappingcells 732, 734, and 736.

In some embodiments, the columns of strapping cells 732, 734, and 736have a configuration similar to the column of strapping cells 542S,544S, 546S, and 548S of FIG. 5. In some embodiments, two adjacentstrapping cells of the columns of strapping cells 734 corresponding tostrapping cells 542S and 544S are separated from two adjacent strappingcells of the columns of strapping cells 732 corresponding to strappingcells 542S and 544S by two rows of ROM cells of memory array 714 andfrom two adjacent strapping cells of the columns of strapping cells 736corresponding to strapping cells 542S and 544S by two rows of ROM cellsof memory array 716.

In some embodiments, the columns of strapping cells 732, 734, and 736have a configuration similar to the column of strapping cells 612S,614S, 616S, and 618S of FIG. 6. In some embodiments, two adjacentstrapping cells of the columns of strapping cells 734 corresponding tostrapping cells 612S and 614S are separated from two adjacent strappingcells of the columns of strapping cells 732 corresponding to strappingcells 612S and 614S by two rows of ROM cells of memory array 714 andfrom two adjacent strapping cells of the columns of strapping cells 736corresponding to strapping cells 612S and 614S by two rows of ROM cellsof memory array 716.

In some embodiments, at least one column of the columns of strappingcells 732, 734, and 736 has a configuration similar to the column ofstrapping cells depicted in FIG. 5, and, at least another one column ofthe columns of strapping cells 732, 734, and 736 has a configurationsimilar to the column of strapping cells depicted in FIG. 6.

For example, in some embodiments, the column of strapping cells 734 hasa configuration similar to the column of strapping cells 612S, 614S,616S, and 618S of FIG. 6; and the columns of strapping cells 732 and 736have a configuration similar to the column of strapping cells 542S,544S, 546S, and 548S of FIG. 5. In some embodiments, two adjacentstrapping cells of the columns of strapping cells 734 corresponding tostrapping cells 612S and 614S are separated from two adjacent strappingcells of the columns of strapping cells 732 corresponding to strappingcells 542S and 544S by two rows of ROM cells of memory array 714 andfrom two adjacent strapping cells of the columns of strapping cells 736corresponding to strapping cells 542S and 544S by two rows of ROM cellsof memory array 716.

In some embodiments, the columns of strapping cells edge strapping cells742 and 744 are edge well strapping cells. Edge well strapping cellsinclude conductive structures configured to receive one or more biasingvoltages and apply the one or more biasing voltage to one or morecorresponding well regions used to form the transistors of Memory device700. In some embodiments, the columns of strapping cells edge strappingcells 742 and 744 are combined edge strapping cells, and each one of thecombined edge strapping cells includes an edge well strapping cell and astrapping cell depicted in FIG. 6.

In accordance with one embodiment, a memory circuit includes a firstmemory cell and a second memory adjacent to the first memory cell. Thefirst memory cell includes a pass device; a word line segment; a firstword line strapping line segment electrically coupled with the passdevice of the first memory cell and the word line segment of the firstmemory cell; and a second word line strapping line segment. The secondmemory cell includes a pass device; a word line segment; a first wordline strapping line segment; and a second word line strapping linesegment electrically coupled with the pass device of the second memorycell and the word line segment of the second memory cell. The first wordline strapping line segment of the first memory cell and the first wordline strapping line segment of the second memory cell are connected witheach other at a first interconnection layer of the memory circuit. Thesecond word line strapping line segment of the first memory cell and thesecond word line strapping line segment of the second memory cell areconnected with each other at the first interconnection layer of thememory circuit.

In accordance with another embodiment, a memory circuit includes a firstmemory cell, a second memory cell adjacent to the first memory cell, athird memory cell, a fourth memory cell adjacent to the third memorycell, a first strapping cell between the first memory cell and the thirdmemory cell, and a second strapping cell between the second memory celland the fourth memory cell. The first memory cell includes a pass deviceand a word line segment. The second memory cell includes a pass deviceand a word line segment. The third memory cell includes a pass deviceand a word line segment. The fourth memory cell includes a pass deviceand a word line segment. The first strapping cell includes a first gatestructure connecting a gate structure of the pass device of the firstmemory cell and a gate structure of the pass device of the third memorycell; a word line segment connecting the word line segment of the firstmemory cell and the word line segment of the third memory cell; a firstword line strapping line segment electrically coupled with the firstgate structure of the first strapping cell and the word line segment ofthe first strapping cell; and a second word line strapping line segment.The second strapping cell includes a first gate structure connecting agate structure of the pass device of the second memory cell and a gatestructure of the pass device of the fourth memory cell; a word linesegment connecting the word line segment of the second memory cell andthe word line segment of the fourth memory cell; a first word linestrapping line segment; and a second word line strapping line segmentelectrically coupled with the first gate structure of the secondstrapping cell and the word line segment of the second strapping cell.The first word line strapping line segment of the first strapping celland the first word line strapping line segment of the second strappingcell are connected with each other at a first interconnection layer ofthe memory circuit. The second word line strapping line segment of thefirst strapping cell and the second word line strapping line segment ofthe second strapping cell are connected with each other at the firstinterconnection layer of the memory circuit.

In accordance with another embodiment, a memory circuit includes amemory circuit includes a first memory cell, a second memory celladjacent to the first memory cell, a third memory cell, a fourth memorycell adjacent to the third memory cell, a first strapping cell betweenthe first memory cell and the third memory cell, and a second strappingcell between the second memory cell and the fourth memory cell. Thefirst memory cell includes a pass device; an isolation device; and aword line segment. The second memory cell includes a pass device; anisolation device; and a word line segment. The third memory cellincludes a pass device; an isolation device; and a word line segment.The fourth memory cell includes a pass device; an isolation device; anda word line segment. The first strapping cell includes a first gatestructure connecting a gate of the pass device of the first memory celland a gate of the pass device of the third memory cell; a second gatestructure connecting a gate of the isolation device of the first memorycell and a gate of the isolation device of the third memory cell; a wordline segment connecting the word line segment of the first memory celland the word line segment of the third memory cell; a word linestrapping line segment electrically coupled with the first gatestructure of the first strapping cell and the word line segment of thefirst strapping cell; and an isolation gate strapping line segmentelectrically coupled with the second gate structure of the firststrapping cell. The second strapping cell includes a first gatestructure connecting a gate of the pass device of the second memory celland a gate of the pass device of the fourth memory cell; a second gatestructure connecting a gate of the isolation device of the second memorycell and a gate of the isolation device of the fourth memory cell; aword line segment connecting the word line segment of the second memorycell and the word line segment of the fourth memory cell; a word linestrapping line segment electrically coupled with the first gatestructure of the second strapping cell and the word line segment of thesecond strapping cell; and an isolation gate strapping line segmentelectrically coupled with the second gate structure of the secondstrapping cell. The isolation gate strapping line segment of the firststrapping cell and the isolation gate strapping line segment of thefirst strapping cell are connected with each other at a firstinterconnection layer of the memory circuit. The word line strappingline segment of the first strapping cell is at the first interconnectionlayer of the memory circuit. The word line strapping line segment of thesecond strapping cell is at the first interconnection layer of thememory circuit.

A number of embodiments have been described. It will nevertheless beunderstood that various modifications may be made without departing fromthe spirit and scope of the disclosure. For example, various transistorsbeing shown as a particular dopant type (e.g., N-type or P-type MetalOxide Semiconductor (NMOS or PMOS)) are for illustration purposes.Embodiments of the disclosure are not limited to a particular type.Selecting different dopant types for a particular transistor is withinthe scope of various embodiments. The low or high logic value of varioussignals used in the above description is also for illustration. Variousembodiments are not limited to a particular logic value when a signal isactivated and/or deactivated. Selecting different logic values is withinthe scope of various embodiments. In various embodiments, a sourceterminal of a transistor can be configured as a drain terminal, and adrain terminal can be configured as a source terminal.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a first memory celladjacent a second memory cell, the first memory cell comprising a firstpass transistor, and the second memory cell comprising a second passtransistor; forming a first word line strapping line over the firstmemory cell and over the second memory cell in a first metallizationlayer, wherein the first word strapping line is electrically connectedto a gate of the first pass transistor and to a gate of the second passtransistor; forming a second word line strapping line in the firstmetallization layer; and forming a first word line extending over thefirst word line strapping line and the second word line strapping linein a second metallization layer, wherein the first word line iselectrically connected to the first word line strapping line.
 2. Themethod of claim 1, wherein the first word line strapping line is free ofelectrical connection to the second word line.
 3. The method of claim 1,further comprising forming a third memory cell adjacent the first memorycell and a fourth memory cell adjacent the second memory cell, whereinthe first word line strapping line is formed extending into the thirdmemory cell and fourth memory cell.
 4. The method of claim 1, furthercomprising forming a gate contact on the gate of the first passtransistor, wherein the first word line strapping line is formed on thegate contact.
 5. The method of claim 4, further comprising forming a viaon the first word line strapping line, wherein the via is formeddirectly over the gate contact, wherein the first word line is formed onthe via.
 6. The method of claim 1, further comprising forming a firstbit line in the first metallization layer extending into the firstmemory cell and electrically connected to the first pass transistor,wherein the first bit line is adjacent the first word line strappingline.
 7. The method of claim 1, further comprising forming a voltagereference line in the first metallization layer extending into the firstmemory cell and electrically connected to the first pass transistor,wherein the voltage reference line is adjacent the second word linestrapping line.
 8. The method of claim 1, wherein the first word linestrapping line is adjacent the second word line strapping line.
 9. Amethod comprising: forming a first pass transistor and a second passtransistor on a substrate, wherein the first pass transistor comprises afirst gate and the second pass transistor comprises a second gate,wherein the first pass transistor is adjacent the second passtransistor; forming a first gate structure extending over the first passtransistor, wherein the first gate structure is electrically connectedto the first gate; forming a second gate structure extending over thesecond pass transistor, wherein the second gate structure iselectrically connected to the second gate; forming a first word linestrapping line extending over the first gate structure and over thesecond gate structure, wherein the first word line strapping line iselectrically connected to the first gate structure; forming a secondword line strapping line extending over the first gate structure andover the second gate structure, wherein the second word line strappingline is electrically connected to the second gate structure; forming afirst word line extending over the first gate structure and over thefirst word line strapping line, wherein the first word line iselectrically connected to the first word line strapping line; andforming a second word line extending over the second gate structure andover the second word line strapping line, wherein the second word lineis electrically connected to the second word line strapping line. 10.The method of claim 9, wherein the first word line is formed extendingover the second word line strapping segment.
 11. The method of claim 9,wherein the second word line strapping line is adjacent the first wordline strapping line.
 12. The method of claim 9, wherein the first wordline strapping line is adjacent the first pass transistor.
 13. Themethod of claim 9, further comprising: forming an isolation device onthe substrate, wherein the isolation device comprises a third gate;forming a third gate structure extending over the isolation device,wherein the third gate structure is electrically connected to the thirdgate; and forming a voltage reference line extending over the first gatestructure and over the second gate structure and over the third gatestructure, wherein the voltage reference line is electrically connectedto the third gate structure.
 14. The method of claim 13, wherein asource terminal of the first pass transistor is electrically connectedto the voltage reference line.
 15. The method of claim 13, wherein asource terminal of first pass transistor is electrically isolated fromthe voltage reference line.
 16. The method of claim 13, wherein theregions directly above the third gate structure are free of the firstword line strapping line and the second word line strapping line.
 17. Amethod comprising: forming a first fin structure over a substrate;forming a second fin structure over a substrate; forming a first gatestructure extending over the first fin structure and the second finstructure; forming a plurality of word line strapping lines extendingover the first gate structure, wherein at least one word line strappingline of the plurality of word line strapping lines is electricallyconnected to the first gate structure, wherein a first word linestrapping line of the plurality of word line strapping lines is adjacentthe first fin structure, and wherein a second word line strapping lineof the plurality of word line strapping lines is adjacent the second finstructure; and forming a plurality of word lines extending over theplurality of word line strapping lines, wherein each word line of theplurality of word lines is electrically connected to at least one wordline strapping line of the plurality of word line strapping lines. 18.The method of claim 17, further comprising forming a second gatestructure extending over the first fin structure and the second finstructure, wherein the plurality of word line strapping lines is formedextending over the second gate structure.
 19. The method of claim 17,further comprising: forming a second gate structure extending over thefirst fin structure and the second fin structure, wherein the pluralityof word line strapping lines is formed extending over the second gatestructure, wherein at least one word line strapping line of theplurality of word line strapping lines is electrically connected to thesecond gate structure.
 20. The method of claim 17, wherein the firstword line strapping line is free of electrical connection to the secondword line strapping line.